Walking a pup isn't hard on it's hips, as long as the pup isn't genetically predisposed to Hip Dysplasia.And if it is genetically predisposed to Hip Dysplasia, it's going to develop Degenerative Joint Disease no matter what you do.

Instead of worrying about what activities might be too physically demanding of a pup, it's better to always be cognizant of how much fun the pup is having. And always stop, while the pup is wanting more.

No matter what activity you are engaging in as play, (and play is all that a pup is capable of) consistently doing it until the pup loses interest and quits, is teaching the pup to hate that activity.